Arcgh no edit button
So to expand a bit, if you look at that diagram doing the rounds on fb about where Corbyn's going to get his money, a lot of it will be from Corporation tax increases (because, you know, those chaps who risk everything to create a business and do one of the most morally good things you can do in our society which is create jobs for you and I are _just_evil_and_greedy_toffs). Take money from companies and they'll be able to employ fewer staff and expand less rapidly or not at all or even contract.
Another source is closing down tax loopholes. Well that's an ongoing battle with extremely complex legislation covering many countries, so that money isn't going to become immediately available if at all.
Corbyn's like a kid in a candy store grabbing everything he can see, whilst only having 10p in his scrotty pocket.